Spacecraft
Launch of first rover, Spirit: June 10, 2003
Spirit's arrival on Mars: Jan. 3, 2004

Launch of second rover, Opportunity: July 7, 2003
Opportunity's arrival on Mars: January 24, 2004

Science instruments: Panoramic camera, miniature thermal emission spectrometer, Mössbauer spectrometer, alpha proton X-ray spectrometer, microscopic imager

Overview

Two powerful new Mars rovers are on the red planet. With far greater mobility than the 1997 Mars Pathfinder rover, these robotic explorers may trek as much as 40 meters (44 yards) across the surface in a day. Each rover carries a sophisticated set of instruments to search for evidence of liquid water that may have been present in the planet's past. The rovers are identical to each other, but will land at different regions of Mars.

The landing for each resembled that of the Pathfinder mission. A parachute deployed to slow the spacecraft, rockets fired to slow it further just before impact, and airbags inflated to cushion the landing. Upon reaching the surface, the spacecraft bounced about a dozen times. When it stopped, the airbags deflated and retracted and the petals opened up, bringing the lander to an upright position and revealing the rover.

The landed portion of the mission features a design dramatically different from Mars Pathfinder. Where Pathfinder had scientific instruments on both the lander and the small Sojourner rover, these larger rovers will carry all their instruments with them. Immediately after landing, each rover will begin reconnaissance of the landing site by taking a 360-degree visible color and infrared image panorama. Then they will each leave the petal structure behind, driving off to begin exploration.

Using images and spectra taken daily from the rovers, scientists will command the vehicle to go to rock and soil targets of interest and evaluate their composition and their texture at microscopic scales. Initial targets may be close to the landing sites, but later targets can be far afield. These rovers will be able to travel almost as far in one Martian day as the Sojourner rover did over its entire lifetime.

Rocks and soils will be analyzed with a set of five instruments on each rover, and a special device called the rock abrasion tool will be used to expose fresh rock surfaces for study. Each rover has a mass of nearly 180 kilograms (about 400 pounds). The prime mission for each rover will last three months on the surface.

More Information:
Athena science package home page
Mars Exploration Rover mission page
NASA's rover fact sheet